The present invention relates to machines for repairing or reconditioning railroad rights-of-way, and more specifically relates to a mechanism for automatically and accurately setting rail tie plates upon the upper surfaces of rail ties.
The invention disclosed in the present application is related to the invention disclosed in copending application Serial No. 07/203,328, filed June 7, 1988, titled "Automatic Tie Plate Sorting Conveyor," Ser. No. 07/224,486, filed July 26, 1988, titled "Automatic High Speed Tie Plate Reorienting System", Ser. No. 07/226,761, filed Aug. 1, 1988, titled "Automatic Tie Plate Setting Machine" and U.S. Pat. No. 4,727,989, titled "Automatic Tie Plate Orientation Sensing System".
Tie plates are used to secure rails to railroad ties and comprise a generally flat steel plate with a substantially flat bottom, spike holes and an upper surface having rail securing ribs. The tie plate upper surface is slightly angled to provide a rail seat canted inwardly, with more mass located on the field side of the plate to compensate for the force distribution of trains negotiating curves at high speed.
In the process of reconditioning railroad rights-of-way, the existing rail is removed along with the tie plates, the ties are replaced or resurfaced, and the track bed is refurbished. Before new rails are laid, replacement or recycled tie plates must be accurately positioned upon the ties.
Tie plate replacement is a cumbersome and labor intensive operation, due to the significant weight of the individual plates 18-40 pounds each) and the rapid rate at which they must be positioned to keep up with the other operations of track reconditioning, most of which are largely automated. It has been estimated that a member of a plate feeding crew will handle 150,000 pounds per eight hour shift. Accurate plate placement is critical, for the plates are required to be positioned within 1/4 inch of an optimum location on the ties. In order to achieve this level of accuracy, a pregager machine with a registration edge follows the plate setting laborers to accurately position the plates upon the ties.
Previous attempts at automating the tie plate setting operation have resulted in devices which lack the capability of accurate placement at the rate of 30 to 40 plates per minute at which automatic tie plate setters must operate to keep up with other automated track maintenance equipment.
Accordingly, the plate setting mechanism of the invention is designed to set tie plates accurately to gage at high production rates in the range of at least 40 plates per minute. In addition, the machine is designed with a minimum of moving parts for greater reliability, can accommodate a large spectrum of tie plate size configurations, and may be integrated with a larger plate handling vehicle traveling at a constant speed over the rail bed.